0:09Skip to 0 minutes and 9 secondsWhat do they weigh? About 100 kilos. And what holds them up? Four cables. How do they adjust the angle of the cables? Two turnbuckles in the front cables. And how are they connected to the cable? Shackles like this. Is it safe? An engineer must have checked the system out. In your design tasks from this week, you will specify the cables and shackles for supporting a loudspeaker system like this one. To do this, you will need to know about forces and how they add. And you will need to know about equilibrium. A force is an abstract concept. Engineers interpret what they see through this concept. It's part of their ‘engineers’ eyes’.

0:57Skip to 0 minutes and 57 secondsExperiments in this week will provide experience of the physical world for you to analyse as you develop your understanding of the concept of forces and how to construct and use free-body diagrams. Then you will be ready for the design task.

Design for strength and safety

By the end of this week you will be able to share the wry smile of engineers as they downplay their capabilities with this self-deprecating definition of structural engineering:

“Structural engineering is the art of moulding materials we don’t wholly understand, into shapes we can’t fully analyse, so as to withstand forces we can’t really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance.” …James E. Amrhein - Masonry Institute of America (Retired) LQEngineer (talk) 03:58, 1 September 2009 (UTC)

Engineers’ immense capabilities are sneakily hidden within the innocuous phrase “in such a way”. You are going to learn something of that understated way. But how?

This brief video will explain.

Talking points

What do you think James E. Amrhein had in mind when he wrote the above message?